Japanese Patent Publication No. 2002-357283 (patent literature 1) discloses an invention of a single lever type water faucet, arranged in an end part of a water supply tube and a hot water supply tube of water service, in which is arranged a piston, inside a tube between the water supply tube and the hot water supply tube, and the water faucet, to avoid occurrence of water hammer. The water hammer preventing device described in the patent literature 1 is arranged in a vicinity of a water faucet of a water supply tube and a hot water supply tube in which a fluid flows in one direction; and is supposed to avoid occurrence of water hammer in the water supply tube and the hot water supply tube.
Japanese Patent Publication No. 2005-208712 (patent literature 2) discloses an invention of a method of opening without water hammer for a fluid flowing passage in which a fluid flows in one direction. In the method of opening without water hammer described in the patent literature 2, a vibration sensor is arranged in an upstream of an actuator operation type valve to detect a vibration Pr; and a control is performed to the actuator operation type valve so that the detected vibration signal Pr becomes approximatively zero. The vibration sensor is arranged in an upstream vicinity of the actuator operation type valve.
Japanese Patent Publication No. 2008-274871 (patent literature 3) discloses a water hammer suppressing device which suppresses water hammers occurring in a main conduit (a flow path in which a fluid flows in one direction) of an inline hydraulic turbine in a hydraulic power plant. The water hammer suppressing device described in the patent literature 3 is provided in a vicinity of the inline hydraulic turbine with a bypass tube, which bypasses the inline hydraulic turbine, and a rupture disc. The water hammer suppressing device described in the patent literature 3 is to suppress water hammers occurring as a result of abruptly suppressing inflow amount into the inline hydraulic turbine, as the rotation speed of the inline hydraulic turbine increases when a power generator of the inline hydraulic turbine is separated from the system, due to an accident or the like; and to verify occurrence of water hammer afterwards.